To investigate the effect of relative proportions of tryptophan in the diet of human subjects. The basal diet, which is similar to one that was useful in studying effect of relative proportions of lysine, will contain adequate amounts of essential amino acids supplied in part by cereals (corn, rice, wheat) and in part by crystalline amino acids. Tryptophan levels will vary from 750 mg per day, as found in the complete mixture, 59 250 mg which is present in the basal diet. Lysine and tryptophan have been selected for initial study of relative proportions because both tend to be limiting in cereals. To obtain further evidence concerning the effect of relative amounts of essential amino acids when fed in crystalline form and when supplied by foods. Initially all data obtained in this project and available in the literature will be analyzed. Then an experiment will be designed to clarify this question which is significant because foods, alone or supplemented with other foods or individual amino acids, will continue to be the principal means of meeting world protein needs although mixtures of amino acids will be used therapeutically. Furthermore, the relative proportions of essential amino acids present in foods differ from those which have been established as minimal requirements when crystalline amino acids were fed. This information should also be useful in estimating tolerance for certain amino acids that must be consumed in excess in order to provide variable amounts of the amino acids most likely to be limiting.